#include<stdio.h>
int main()
{
	int i,arr[10];
	int sum=0;
	float average;
	for(i=0;i<10;i++)
	{
		scanf("%d",&arr[i]);
		sum+=arr[i];
		average=sum*1.0/(i+1);
	}
	printf("%f",average);
	return 0;
}
 
